Construct a quadrilateral ABCD in which AB = 7.7 cm,

Steps of construction:

Step I: Draw DC $=5.1 \mathrm{~cm} .$

Step II : Construct $\angle \mathrm{DCB}=120^{\circ}$.

Step III : With C as the centre and radius $6.8 \mathrm{~cm}$, cut off BC $=6.8 \mathrm{~cm} .$

Step IV : With B as the centre and radius $7.7 \mathrm{~cm}$, draw an arc.

Step V : With D as the centre and radius $3.6 \mathrm{~cm}$, draw an arc to intersect the arc drawn in Step IV at A.

Step VI : Join $A B$ and $A D$ to obtained the required quadrilateral.